The present invention relates to improved aspirin formulations, and more specifically relates to an improved constant release aspirin formulation which is readily reproducible on a commercial basis.
Attempts to develop a timed release aspirin product which will provide a more constant level of aspirin in the blood over a prolonged period of time have been in progress since at least 1953. (See Press, U.S. Pat. No. 2,953,497.) and a substantial body of prior art exists which is directed specifically to timed or sustained release aspirin formulations, also referred to as prolonged release, constant release, controled release and the like. See, for example, U.S. Pat. Nos. 3,488,418, 3,341,416, 3,155,590, 3,247,066, 3,115,411, 3,632,739, 4,012,498, 3,362,881, 4,308,251 and commonly assigned U.S. Pat. No. 4,375,468.
Commonly assigned Guy et al U.S. Pat. Nos. 4,025,613 and 3,906,086 disclose one such product, a timed-release aspirin tablet which is made by coating particles of aspirin prior to tabletting with cellulose acetate phthalate and a plasticizer. While aspirin tablets prepared by the process of the Guy et al patents exhibit the desired in vitro constant release properties, and satifactory tablets are produced in experimental quantities, difficulties are encountered in larger, commercial production runs.
The present invention provides an improved cellulose acetate phthalate-plasticizer matrix formulation which not only exhibits the desired constant release rate properties, but eliminates the problems encountered with the Guy et al process and formulations when aspirin tablets are produced in large batches, as is necessary for commercial production.